So I bought two 12 packs of traditional ice cream sandwiches, some local strawberries, some bananas, some ice cream toppings; strawberry, caramel and chocolate to be exact and two tubs of Cool Whip (though I only needed one).
First I layered the bottom of the pan/dish with ice cream sandwiches. I had to cut them to fit properly. Then I covered those up with a layer of Cool Whip and tossed it into the freezer while I prepped by strawberries and bananas (and by prepped I mean washed and sliced).
I then put down a layer of strawberries and topped those with a layer of bananas. Upon completion of this I drizzled on some strawberry sauce. Here's a photo up to this point.
Next, I added a second layer of the ice cream sandwiches, again cutting them so they'd all fit (see diagram).
Then I topped it with Cool Whip again and drizzled all three sauces on top (I'm crazy like that)! I tossed it in the freezer for a few hours before we ate it, but I'm sure you could make this the night before a party and pop it in the freezer. I'd assume you'd need to leave it out for 15 minutes or so to allow it to soften up for cutting. It's a goobley, gobbley mess, but man this Banana Split Ice Cream Sandwich Cake was uber delicious!
Of course you can pretty much use any thing for the centre. Chocolate bars, white chocolate, peanut butter cups, fruit, flavoured Cool Whip....anything your imagination can come up with I'm sure. Mmmm, white chocolate and raspberries would be amazing! Maybe next time. What would you use???